Capacity of Enzymes of the Euphorbiacea Aleurites montana Involved in CO
2- Fixation, Compared to Plants HavingC
3-, C
4- and Crassulacean Acid Metabolism
Norbert Grotjohann
a, Ping He
band Georg H. Schmid
a,*
a Lehrstuhl für Zellphysiologie, Fakultät für Biologie, Universität Bielefeld, Postfach 10 01 31, 33501 Bielefeld, Bundesrepublik Deutschland.
Fax: +49 (521) 1066410. E-mail: G.Schmid@Biologie.Uni-Bielefeld.de
b Central South Forestry University, Zhuzhou/Hunan 41206, People’s Republic of China
* Author for correspondence and reprint requests
Z. Naturforrsch.55 c, 383Ð391 (2000); received March 2/April 7, 2000 Dedicated to Professor Wilhelm Menke on the occasion of his 90thbirthday Aleurites montana, Phosphoenolpyruvate Carboxylase, Malic Enzyme, Malate Dehydrogenase, Ribulose Bisphosphate Carboxylase
Capacities of phosphoenolpyruvate carboxylase (PEP-Co), ribulose bisphosphate carbox- ylase (Rubisco), NADP+malic enzyme (ME) and of malate dehydrogenase (MDH) were measured in the EuphorbiaceaAleurites montana,grown under 700 ppm CO2for four weeks prior to enzyme extraction. For comparisonBryophyllum daigremontiana(CAM),Saccharum officinarum(C4) andCapsicum frutescens(C3) were treated in the same way. PEP-Co capac- ity of Aleuriteswas in the range of 12-, that of Capsicumapprox. 26 nmol ¥ minÐ1¥ mg proteinÐ1, without significant influence of the light period or CO2-treatment. In contrast, the activity of the enzyme fromSaccharumwas, depending on the duration of light, 160- respec- tively 96 times higher than that of the tung-oil tree. InBryophylluma rather low activity in the morning was increased during the day to approx. 230 nmol¥minÐ1¥mg proteinÐ1in plants grown in the greenhouse and to approx. 115 nmol¥ minÐ1 ¥mg proteinÐ1in those from the growth chamber. Malate was hardly detectable in extracts ofAleurites, whereas it was high inBryophyllum, depending on the light period. The ratio of average PEP-Co to Rub-Co capacity was high for the CAM-plant (20:1), somewhat lower for sugar cane (10:1), but almost at equality forAleurites(0.9:1) and chilli (0.8:1). For the NADP+malic enzyme, low capacity (20 to 28 nmol¥minÐ1¥mg proteinÐ1) was found forAleuritesand forCapsi- cum, whereas it was 10 to 17 times higher in Saccharum. InBryophyllum,the activity was up to 80 nmol¥minÐ1¥mg proteinÐ1, dependent on light period. MDH capacity was ex- tremely high in all plants investigated. Highest rates (10Ð20µmol¥minÐ1¥mg proteinÐ1), were obtained for Bryophyllum, followed by sugar cane and Capsicum with 5Ð8 µmol ¥ minÐ1 ¥ mg proteinÐ1. Again, the lowest capacity was found in extracts of Aleuriteswith approx. 1.3 to 1.6µmol¥minÐ1¥m proteinÐ1. Thus, inAleurites montanano indication for C4- or Crassulacean acid metabolism was obtained. Therefore, the earlier observed very efficient uptake of CO2cannot be explained by a high expression of the PEP-Co protein, known to occur in CAM- and C4-plants.
